Trailing antenna



Dec. 9, 1947. F. J. B ERB ERlCl -l, JR 2,432,371

TRAILING ANTENNA Filed Nov. 3, 1942 INVENT feA/yz J 552,950 12.

Patented Dec. 9, 1947 Eranlr'ld. Berberich; Jr., Los Angclcs;mGa-lif.,.asr=

signer to" Douglas Aircraft: Gompanm; Inc.

Santa-Monica, :Calif.

ApplioationNovember a, 1942; SerialNo, 464;395"

' tennis. (01-. 25111 -33) This: invention relatesuto. an improvedttrailts ing: antenna foruse in an. airplane; zwhich hros vides means extensible; beyond. the surface: of the airplane. fuselage toprevent. gyrations" of the antenna weight and keep it from striking the fuselagewhile the antenna:isibeingrreeled inwardly or' outwardly therefrom:

In; all airplanes it iszhighly advantageousto have: an exterior" trailing. wire: antennaisince; a fixed. wire antenna, attached.rigi'dly'r'ateach end to'some' portion of the airplane; is: necessarily limitedin physical length... Since most" airplanes are of: such. size'as *toprevent? the useioff ajfixed' antenna; having. dimensions approximately equal to even a quarter wave antennaatcurrentiy 2i invention comprises: a. flexibletrailing antennacabla-andia rod se'curedito the outer end thereofftowhicha lead weight issaattachedi. The antenna.isrsiidablesthrough a iairlead which proje'cts'iiromthetlowen-portion otthe airplane fuselage in asfrearwa'rdly. inclined position; so the made-i telescopicain:ordenthat; the antenna and established aviation radio frequencies, the most I satisfactory antenna isin'th'e'iorm of aweighted wire or cable which maybe paid out. from a reel into the airstream varied? distances" depending upon the radio frequency usedand the distance between sender and receiver. It isnecessaryto reel such an antenna into the 'airplane'bef'ore landingin' order" to" avoid entanglement of the antenna.- and'weight on trees. or othen objects. as the airplane is i approachingtherunway. l

Considerable difiiculty has been experienced in developing; a: trailing antenna for'airplanes which" can be reeled in or out of the fuselage without becoming entangled" with adjacent-"pro? jecting. parts of the airplane such as marker lights, landing gear and even the? control surfaces; of the empennage. A trailing antenna consisting of a. weighted flexible cable or wine will develon oscillatory and: gyratory movements of excessive amplitude. when its outerweighted end is brought. close to the airrilariefuselage at air; speeds of onehundred.andthirty miles per hour ormore. As, the speed. of the-"airplane increases and/or. the weighted end is broughtin closer proximity to the airplane; the gyrations increase in intensity: Suchv gyratory movements cause the lead weight attached to the end of the antenna to violently strike the fuselage and projecting objects sometimes resulting in serious damage. Continued swinging of the Weight at the end of the flexible. cable antenna also may result in breaking of. th -cable at the connection to the weight, dropping the weight to the ground. Experiments carriedon in an efiort-toeliminate gyration, ofthe antenna and antenna weight at a distance from the fuselage where it is. beyond the zone of air turbulence; near the-airplane does not solve. the problernqsince a-fairlead' of a length to iulfillthispurpose would projectbelow the ground line oithe landinggear and. would objectionably increase the; drag of the airplane.

fairleadr'be drawn' into. th fuselage when not; inwuse; eliminating the drag caused thereby:

One object: ofr'this". invention is'to provide a means. for" eliminating oscillatory: and gyratory movements. of: the; weight: of a. flexible trailing antenna.

' Another; objectiofthis'invention isto provide 313K061 atthe: end of the: flexible antenna retract? able iupwardlythrough the fairlead', which substantially' eliminates movements of the weight figed'theretowhen the weight is-close to the fuselage-andwhich *dampsithe' weight movements at morereznote positions, sufficiently'to cause the rod: and; weight: t'o= be" practically unaffected by air turbulence:

Further obj acts; andadvantages of: the invention will be brought out in the following description taken in-connectio'n' with theaccompanyingi drawings and" appended claims.

Referring; now: to the drawings,

Figure 1: is a; side elevation of an airplane with a-portion of the-fuselageout away'showing the antennain two extended: positions in dotted lines and inl fully retracted position insolid lines.

Figure? is; a side" elevation of: the rod and weight;

Figure 3; isa sectiontaken through the weight toshow method of;- attaching theweight to the rod-.-

- Figure; 4; is an endview of' the, weight.

As'best shown;- in Figure 1' of the drawings, an airplane-Innis shown having empennage I2 and a fuselage Ml 'Acfairlead IB'is secured to the fuselage: and: setq'in a rearwardlyr inclined positionwithrespect thereto. A reeling mechanism' L8. is; placed: immediately above and n line with the fairlead so that a flexible antenna 28 Wound amund'a reel12-2aonthe reeling mechanism may pass through thef'airlead I16.

As-maybe-seemin Figures 2; 31and'4, the flexible; antenna. is secured to a loop 24 on an attachment: sling- Z8; Secured to a second loop 33 on-the outer end;o f attachment sling: 26 is'a: rod 2d preferably-ofa material ofrelatively low specific "gravity. and relatively high rigidity; structural strength and fatigue qualities. The cross sectional area-"of the rod is as small as may.- be; without: sacrificing: rigidity and" strength. To, the outer; end-- of the. rod 28. is secured a it weightv 3 The weight 32 is bored at 35 to slidably receive the rod 28 and counter-bored at 36 to receive a spring 38 which is seated under compression between the inner end Wall of the counterbore and a collar 40 on the outer end of the rod 28.

A threaded plug 42 closes the outer end of the counterbore 35 and limits outward movement of the collar 49 under the action of spring 38.

In operation as shown in Figure 1 of the drawings, the pilot manually or by motor causes the antenna to be paid outwardly into the airstream through the fairlead i5, lowering the rod 28 and weight 32 by gravity. The rod 2'8 is guided by the fairlead I9 which holds the weight attached thereto against lateral movement caused by the turbulent airstream outside the fuselage.

The zone of air turbulence adjacent the fuselage comprises an inner zone of greater turbulence and an outer zone of turbulence which, while markedly less violent than that of the inner zone, is yet sufiiciently strong to cause movements of the weight of dangerous amplitude. The rod 23 and projecting portion of the fairforce causing the antenna when paid out to assume a trailing position relative to the airplane as shown in dotted lines, Figure 1. In this manv ner, it is possible to reel the antenna in or out lead It are sufiiciently long to place the weight I 32 outside of the inner turbulent zone when the inner end portion of the rod'is disposed in the outer end portion of the fairlead, just sufficiently to have a telescopic overlying relationship. Thus,

if the fairlead project 22 inches from the fuselage and the rod is 28 inches long, the rod holds the Weight substantially rigid against air turbulence as long as the weight is not over approximately 44 inches from the fuselage since at that distance the telescopic overlap of rod and fairlead is 6 inches which may be sufiicient to enable the fairlead to hold the rod in fixed longitudinal alignment therewith. As the inner, more violently turbulent zone may not be more than 36 inches in depth, the weight is held against oscillatory and gyration movements as it passe therethrough during reeling in or paying out of the antenna.

When the rod 28 is entirely outside the fairlead, it and the weight 32 may swing about the outer end of the fairlead as a center. However, the effect of the stiff rod 28 is to damp and slow the swinging movements caused by the air turbulence, reducing their amplitude to a safe value which may be 36 inches or less in an approximately vertical plane. The outer turbulent zone of relatively less violence may extend ten feet from the plane. As the weight passes through this zone either in reeling in or paying out the antenna, its oscillatory movements are reduced to such a low amplitude that the weight will not strike the fu ela e or objects projecting therefrom in view of the distance of the weight from the fuselage after the rod leaves the fairlead.

The outer end ofthe fairlead I6 is bell shaped at 49. When the antenna is reeled into completely retracted position, the rod 28 passes entirely within the fairlead, the weight seats itself in the bell and the tension created in the cable and rod by the reel compresses the spring 38, resiliently holding the weight from lateral play against the bell. Any lateral play of the'weight in. the bell will deform the bell and develop structural weakness in the rod at the end of the weight with the possibility of breaking the bell from the fairlead or breaking the rod from. the Weight.

After the weight on the antenna rod has passed downwardly and rearwardly thru the turbulent without danger of its becoming fouled on the empennage or other parts of the airplane.

The lighter and more rigid the rod, the greater the damping effect when the rod is entirely outside the fairlead and the less apt will the rod be to vibrate within and damage the fairlead when it is in telescopic relation therewith but not entirely retracted. The greater the rigidity and strength of the material of the rod, the smaller and lighter it may be and yet meet the load requirements attendant upon its use and have the rigidity which enhances its ability to perform its function. High fatigue qualities decrease the probability of fracture after extended use.

I claim:

1. In a trailing antenna for an aircraft for use with a reel mounted at the inner end of a fairlead projecting downwardly from the aircraft,

the combination of: a flexible antenna for winding at its inner end upon the reel; a relatively non-flexible and relatively light Weight rod of a substantial length connected to the outer end of the antenna; and a weight connected to the outer end of the rod, the length of the rod being substantially the same as the length of the fairlead, the fairlead receiving the inner end of the rod as the antenna is Wound upon the reel and confining the rod therein, thereby damping the oscillatory and gyratory movements of the weight resulting from air turbulence as the weight is drawn up toward the aircraft.

2. In an antenna device for an aircraft, the combination of: a fairlead carried by the fuselage of the aircraft and projecting outwardly therefrom; a reel mounted to the fuselage of the aircraft at the inner end of said fairlead; a flexible antenna passing through said fairlead and having its inner end secured to said reel; a rigid rod of a length substantially equal to thelength of the fairlead connected to the outer end of the flexible antenna; and a weight of a diameter greater than the diameter of the rod connected to the outer end of the rod, the length of the weight being substantially less than the length of the rod; said fairlead receiving and confining the inner end of the rod therein as the antenna is wound upon the reel, thereby holding the rod and the weight carried thereby against lateral movements resulting from air turbulence as the antenna is wound upon the reel and the weight is drawn toward the aircraft.

FRANK J. BERBERICH, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

